In conventional compression molding it is customary to deposit a preform of predetermined shape and size within the mold cavity, the preform being composed of the material to be molded into the completed molded article. The consistency of the molded material itself is relied upon to cause distribution of the molded material throughout the die cavity. An overflow well circumferentially surrounds the mold, and the excess material overflows into this well, and becomes waste.
In accordance with the foregoing, it is necessary that the preform have a geometry sufficiently similar to that of the mold, so that the molded material will distribute itself sufficiently throughout the mold cavity. Also, when molds with multiple mold cavities are used, it is necessary that an individual preform be deposited within each such mold cavity. This results in a considerable amount of waste, because each cavity is provided with its own overflow well.
Another problem which results from the conventional molds and methods referred to above is that certain consistency limitations are imposed upon the molded material, because the material itself is used to cause the distribution of the material throughout the mold. Frequently a material having different viscosity characteristics would be preferred for the particular application, thus requiring the use of different molding methods, such for example as injection molding or the like. A still further difficulty with the molds referred to above, is that upon occasion the mold cavity may not become completely filled with the molded material due to improper or inadequate flow. This generally requires that excess material be used in the preform, to insure complete filling of the mold, which in turn results in excess waste.